A rendering shows the view from Planet 9 toward the sun. A new theory tries to explain where this potential planet came from.

There's an alien in our midst. An alien planet, that is.

A new theory published this week suggests that the much-debated "Planet 9" isn't just a new member of our solar system, but rather an exoplanet. There is evidence that Planet 9 -- if it exists -- was kidnapped by the sun from its original host star.

As indicated by a new computer simulation developed by astronomers at Lund University in Sweden, our sun may have pulled the exoplanet from its host star as the two passed each other.

"Planet 9 may very well have been 'shoved' by other planets, and when it ended up in an orbit that was too wide around its own star, our sun may have taken the opportunity to steal and capture Planet 9 from its original star," researcher Alexander Mustill said in a news release. "When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the sun."

Earlier this year, researchers discovered the presence of a ninth planet by studying the orbits of icy objects beyond Neptune. They noticed anomalies in the objects' orbits and tracked them -- leading them to the gravitational pull of Planet 9.

The existence of Planet 9 is still unproved, and images have "remained elusive." But astronomers haven't been twiddling their thumbs. They have come up with a few hypotheses for what the planet may look like.

There's much more work to be done to figure out if this is just a theory or the real deal. So, until we know for sure, we'll just keep thinking our solar system is a master thief.